Sex with a dish (5)
I believe the answer is:
viand
'a dish' is the definition.
(I know that viand is a type of dish)
'sex with' is the wordplay.
'sex' becomes 'VI' (VI in Roman numerals - 'sex' is 'six' in Latin).
'with' becomes 'and'.
'vi'+'and'='VIAND'
(Other definitions for viand that I've seen before include "Item of food (arch.)" , "loaf of bread, maybe?" , "something to eat" , "Meat; article of food" .)